US6414746B1 - 3-D imaging multiple target laser radar - Google Patents

Abstract

A three dimensional imaging device is presented which uses a single pulse from a pulsed light source to detect objects which are obscured by camouflage, fog or smoke but otherwise enveloped by a light-transmitting medium. The device simultaneously operates in two modes, light reflected from the nearest object is processed to form a three-dimensional image by an array of pixels. This first image is based upon the light-pulse transit time recorded in each pixel. Each pixel also contains a high-speed analog memory that sequentially stores reflected signals at a repeated time interval. The first reflection acts as a time base that controls when the analog memory begins or ends the storage sequence. The first return could be from a camouflage net and the amplitudes of the return signals, after the first return, would then be from objects behind the net. Computer processing these amplitudes reveals the three-dimensional nature of the obscured objects.

The device consists of the pulsed light source, optics for collecting the reflected light, a sensor for detecting the light and converting it to electrical data, drive and output electronics for timing and signal conditioning of data generated by the sensors and a computer for processing the sensor data and converting it to a three dimensional image. The sensor collects and processes the light data in a unique manner, first converting it to electricity by a number of alternate detector technologies and then using integrated circuit chips which consist of a two dimensional array of electronic pixels also called unit cells. The two dimensional array defines two dimensions of the image. Stored within each unit cells is data associated with the third dimension, ranges of targets, and amplitudes of target reflections. This data is read out of the integrated circuit chip in the time interval between laser pulses to a processing computer. The processing computer corrects the data and, by means of computer algorithms specific to the device, converts the data to a three-dimensional image of one or more targets. This image may be viewed or processed electronically to isolate targets.

Description

FIELD OF THE INVENTION

This invention relates to a laser radar vision apparatus capable of producing three-dimensional images of distant targets located behind reflective or absorbing but penetrable barriers such as camouflage and obscuring smoke. In particular, this invention relates to a multiple pixel, electronic apparatus for capturing three-dimensional images of distant targets, within obscurants, at high-spatial and high-range resolution in the atmosphere or in space with a single laser pulse, using a laser-reflection generated trigger.

BACKGROUND OF THE INVENTION

This application is a continuation-in-part of U.S. patent application Ser. No. 08/665,738, Filed Jun. 19, 1995, 3D Now U.S. Pat. No. 6,133,989 which is a CIP of Ser. No. 08/015,623, Now U.S. Pat. No. 5,446,529 Imaging Laser Radar. Laser radars (ladars) determine range in the atmosphere by measuring the transit time of a laser pulse from the transmitter/receiver to a partially or fully reflective target and dividing by twice the velocity of light in the atmospheric medium. If there are more than one return pulse, only the first return pulse is used in the range processing. Range resolution in such devices is related to the accuracy of the transit time measurement. In the atmosphere, ranges are typically measured in kilometers, where range resolution can be smaller than 30 cm. A 3-D target image can be obtained with a conventional laser radar by rastering the laser beam across the target and measuring the transit time, pulse by pulse, where each pulse corresponds to a point on the target. The distance between points on the target determines the spatial resolution of the rastered image and defines the picture element (pixel) size; the number of pixels at the target determines the pixel-array size; the range resolution determines resolution in the third target dimension. Rastering is a slow process, particularly for large pixel-array sizes, and it requires cumbersome mechanical scanners and complex pixel-registration computer processing. In addition, if the first laser-pulse return is from a partially reflective obscurant, which is hiding the target, then the 3-D image does not reveal the nature of the real target.

U.S. patent application Ser. No. 08/665,738, Filed Jun. 19, 1995, by the present inventors disclosed a lightweight, small-size, multiplexing laser radar receiver, the LR-FPA, that could image an entire target, in the atmosphere or in space, at high-spatial and high-range resolution with a single laser pulse. Thus the necessity of laser rastering or using a multitude of laser pulses to obtain a three-dimensional image is avoided. The reflected laser pulse, from different portions of an object, stop independent clocks located in a two-dimensional array of pixels. The times at which the clocks are stopped are related to the third dimension of the object by the velocity of light and are stored in the pixels along with peak signal data. The time data and peak signal data is read out from the array between laser pulses and used to construct the three-dimensional image. Processing the peak signal amplitude with the time data increases the range resolution accuracy. More than one reflected pulse for each pixel is accommodated by separately storing the return time and peak signal of each reflection.

U.S. Pat. No. 5,446,529, issued Aug. 29, 1995 to the present inventors discloses a lightweight, multiplexing laser radar receiver (3DI-UDAR) that can generate a three-dimensional image of an entire object, in a light conducting medium, such as water or the atmosphere, with a single laser pulse. The imaging is accomplished by integrating and storing the reflected signals from a multitude of range resolution intervals (range bins), independently for each of a two-dimensional array of pixels; each range bin across the two-dimensional array corresponds to a range slice in three dimensions. After reading the range bin data out between laser pulses, the time of laser pulse returned from the object is determined for each range bin in the two dimensional array, by means of the integration clock and the start of integration. The three-dimensional image is constructed by the knowledge of the return time of each two-dimensional slice. Because there is return pulse amplitude information as a function of time rather than just the peak of the return pulse, more information can be derived concerning the character of the target. The first range bin begins storing information in response to a signal from the invention's drive electronics rather than from an external signal such as the first reflection from the light conducting medium (the surface of the water for example).

There is only a finite storage capacity for each of the pixels (typically 30 to 200 storage bins) in the 3DI-UDAR. For high spatial resolution in a medium that does not attenuate the light appreciably, the effective depth from which the information is coming from is only a small proportion of the entire range. For example, for 30 cm range resolution, 200 storage bins may only correspond to a depth of 60 m whereas the absolute range or the ladar may be many tens of kilometers. Turning on the range bin integration at the optimum range position (the target position) could involve a trial and error process requiring more than one laser pulse or another system which first finds the time delay to the target and then transfers that time delay to the drive electronics.

BRIEF DESCRIPTION OF THE PRESENT INVENTION

In the present invention a reflected laser pulse from one or more targets, or from an obscured target are integrated and stored in a sequence of range bins, independently for each of a two-dimensional array of pixels. The range bin integrations are turned on automatically, including a possible programmed delay, as the first reflection arrives at the receiver of the invention. Alternatively the integrations are occurring continuously, with the storage bins being filled by new data until the first reflection arrives. Storage then proceeds until a predetermined but adjustable number of storage bins are filled allowing the option of obtaining data prior to the first reflection and/or after it to be stored. By processing this data, preferably between laser pulses, one or more three-dimensional images of single or multiple targets or targets within obscurants can be generated.

A preferred embodiment of the sensor of the invention is a hybrid of two chips, an array of detectors (or collectors) directly connected to an array of processing-electronics unit cells. Each detector/collector, on one chip, is connected to its own processing-electronics unit cell, on the other chip, and defines a pixel in the image. Each processing-electronics unit cell, on the array, contains an identical and unique integrated circuit which can store the first reflected-pulse transit time, the first reflected peak amplitude and/or a sequence of range bins which contain amplitude information about the first reflected pulse and subsequent reflected pulses or amplitude information only about subsequent reflected pulses. Transit-time and pulse amplitude information for all pixels is read out preferably between laser pulses. Laser photons interact directly with the detector array generating a signal or laser photons are converted to electrons that then generate the signal in different embodiments of the invention.

It is the object of the present invention to provide a device for three dimensional imaging of obscured or unobscured objects using a single laser pulse, in transparent or semi-transparent media by a sequence of measurements on the returned pulse amplitude and to overcome the problems of prior systems associated with the need for first determining the range of the target. The device comprises a pulsed light source, means for projecting the light towards the object, optics for collecting the reflected light, improved sensors for detecting the reflected light, drive and output electronics for timing and signal conditioning of data from the sensors and a computer and software for converting the sensor data to a three dimensional image.

It is further the object of the present invention to provide improved sensors which detect and store laser-pulse, target-reflected, transit-time and/or target-reflected laser pulse amplitude information on a processing-electronics unit cell array from which the ranges and 3-D shape of multiple targets or obscured targets can be accurately determined.

Other objects of the invention will be disclosed in the detailed description or the preferred embodiments that follow and from the claims at the end of this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of the preferred embodiment of the Laser Radar Focal Plane Array Imaging System.

FIG. 2 is a perspective view of the hybrid sensor of the present invention.

FIG. 3 is a side view of the vacuum tube sensor of the present invention.

FIG. 4 is a block diagram of the unit cell processing-electronics of the present invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

A preferred embodiment of the present invention, the Penetrating 3-D Ladar (PDAR) imaging system depicted in FIG. 1, is designed to produce three-dimensional image data (area and range) from a single laser pulse reflected from objects in the atmosphere, located in or behind obscurants, using transit time and/or amplitude information, and process the data to form a three dimensional image. Six parts make up the preferred embodiment of the invention; a pulsed laser1, withdelivery system1a,collimator1bandlaser transmission detector1c;the data processing and laser control system2; thesensor3, and associated Drive and Output Electronics4, and theoptics5. The Drive and Output Electronics4 is electrically connected to animage processing computer4a.

FIG. 2 shows onesensor design3, a hybrid sensor, in greater detail. It consists of adetector array chip6, composed ofindividual detectors7, the laserradar processor chip8, and conducting bumps9, which electrically connect eachdetector7 to a single, corresponding, laser radar processor processing-electronics unit cell10. Wire bond pads11 electrically connect thehybrid sensor3 to the drive and output electronics4 multiplexing and chipoutput amplifier circuitry12 connect the processing-electronicsunit cell circuitry10 with the wire bond pads11. A bump pad fabricated with the last metal layer on the processing-electronics unit cell circuitry connects the metal bump9 to the processing-electronicsunit cell circuitry10. In thehybrid sensor3, laser light interacts directly with the detectors which are solid state devices that are responsive to the particular laser wavelength. The detectors are made on a solid-state substrate14. The detector size can be 1 μm to 500 μm on a side. The array size can be 1×1 to greater than 1024×1024. Typically the chips are a few centimeters square. Thesolid state substrate14 may or may not have lenses etched into it. These lenses allow the detector size and noise to be reduced while maintaining the same collection area. In an alternate design a lens array is placed above thedetector array6 rather than etch lenses into thedetector substrate14.

For intense photon sources thedetector array chip6 may be combined with the laserradar processor chip8 in a monolithic design. In this configuration asmall detector7 would be incorporated in the laser radar processor processing-electronics unit cell10 and no metal bumps would be necessary.

FIG. 3 shows an alternate sensor design, thevacuum tube sensor3, where theanodes23 of an anode array are fabricated using the last layer of metal on the laserradar processor chip8 and enclosed in avacuum tube15. This design eliminates all conducting bumps9 since theanodes23 are part of the processing-electronics unit cells10. Anelectron amplifier24, typically one or more microchannel plates, is positioned between the photocathode andanode23 array.

In an alternate design theanodes23 are fabricated as a separate chip, an anode array chip. Metal pads on top of a substrate, typically ceramic, comprise the anode array chip; theanodes23 collect electrons and pass the electrical signals through metal vias in the ceramic substrate to conducting bumps9 at the underside of the anode array chip. Contact to the conducting bump9 is made at the metal via on the bottom of the anode array chip substrate.

The vacuum tube may contains atransparent window16 to transfer the laser light to aphotocathode17, where the laser light is converted to photoelectrons. Thewindow16 may be optical glass, a fiber optics plate or sapphire. A voltage between the photocathode and theelectron amplifier24 generates an electric field, E1, in the tube to accelerate photoelectrons into theelectron amplifier24. A voltage between theelectron amplifier24 and the anode array generates an electric field, E2, in the tube to accelerate electrons amplified in theelectron amplifier24 into theanodes23 of the anode array. The laserradar processor chip8 is mounted on aceramic chip carrier18 which containswire bond pads19 that communicate with the drive and output electronics4 (FIG. 1) and laserradar processor chip8 by means ofwires20 and pins25. Some high-speed clocks may not be generated on the drive electronics4 but may be generated on the laserradar processor chip8 or on aspecial clock chip22 located inside thetube15 on theheader18. Thevacuum tube15 may also contain guard rings or electrons shields21 at the same potential as the detector array. Typically the FIG. 3 sensor is few centimeters in all three dimensions.

In an alternate design theelectron amplifier24 may not be present. Adetector array chip6, may replace the anode array chip, bump bonded to the laserradar processor chip8, and enclosed in avacuum tube15. In this alternate design a voltage between thedetector array6 and thephotocathode17 accelerates electrons into thedetector array6.

In analternate sensor3 design, the FIG. 3 sensor may be placed in a magnetic field oriented perpendicular to thephotocathode17.

FIG. 4 shows a block diagram of the preferred processing-electronicsunit cell circuitry10. Ananode23 or adetector7 is electrically connected to the processing-electronicsunit cell circuitry10, directly to a Resistive Trans-impedance Amplifier (RTIA)28. The voltage output from theRTIA28 is separated into two legs, one leg, the time-of-first-return (TFR)leg26 is associated with processing and storing the return time of the first laser reflection and the other leg, amplitude-of-return (AR)leg27 is associated with processing and storing all the return amplitudes of reflected laser pulses. The first component in both legs is ahigh pass filter29 and34. In practice this component is usually combined with the next component in the processing sequence to save chip real estate. The amplitude-of-first-return (AFR)leg45 separates from theAR leg27 after thehigh pass filter34. TheAR leg27 is then connected to avoltage amplifier35, then abuffer36 and then to the 3DI-UDAR amplitude-storage circuitry43. TheAFR leg45 connects thehigh pass filter34 to the peak detector andstorage circuitry38, though abuffer37.

Thehigh pass filter29 on theTFR leg26 is connected to avoltage amplifier30, to anotherhigh pass filter31, to a Schmitt Trigger and then to aMemory33. TheMemory33 is connected to the Peak Detector andStorage Circuitry38. TheMemory33 is also connected so it can open theSwitch39. A ramp voltage orclock pulse line53, from the drive and output electronics4, pass thorough theSwitch39 to either an Analog Memory or aPulse Counter40. In alternate designs the ramp voltage or clock pulses are generated on the laserradar processor chip8 or on acontiguous chip22. TheMemory33 is also connected to adelay counter42 which is connected to the 3DI-UDARAmplitude Storage Circuitry43.

All data storage circuitry, the Peak Detector/Storage38, the Analog Memory/Pulse Counter40 and the 3DI-UDARAmplitude Storage Circuitry43 is connected to theOutput Amplifier41. TheOutput Amplifier41 is connected to the drive portion of the drive and output electronics4 by therow line46 and thecolumn line47. Theoutput amplifier41 is connected to the output portion of the drive and output electronics4 by the first-return range line48, the first-returnamplitude peak line49 and therange bin line50. Thedelay counter42 is connected to the drive and output electronics4 by thebin count control51 line and the 3DI-UDARamplitude storage circuitry43 is connected to the electronics4 by the Read/Write andcontrol line52.

The PDAR imaging system functions as follows. A pulsed laser1 (FIG. 1) emits a laser pulse, via adelivery system1aandcollimator1b,towards a target. Alaser transmission detector1cgates on the ramp voltage or clock located within the output and drive electronics4. The collimator is designed so that the laser pulse illuminates all or a large part of the target area and not just one point. Laser light reflected from one or more targets is captured by theoptics5 and focused on thesensor3. Light absorbed by the detectors7 (sensor in FIG. 2 only) of thedetector array6 are converted to electrons and holes and each is conducted by detector internal fields to opposite sides of thedetector substrate14. Charges that conduct to the bottom of thesubstrate14 are conducted through the conducting bump9, as electric currents, to laser radar processor processing-electronics unit cells10 corresponding to thedetectors7 that absorbed the laser photons.

For intense reflected signals or where the size of the laser radar processor processing-electronics unit cell10 is large, a monolithic design can incorporate asmall detector7 into in the laser radar processor processing-electronics unit cell10. Under these circumstances the detector current flows directly into the processing-electronicsunit cell circuitry10.

Under the circumstances that a lens has been etched into thedetector substrate14, or a lens array has been placed above thedetector array6, light is collected by these lenses and focused onto thedetector7 region producing electric currents in thedetectors7 of a larger magnitude than would occur without the lenses, increasing signal-to-noise ratio.

Under the circumstances that thedetector7 is actually a solid-state amplification detector, such as an avalanche diode, the electric current generated in the detector is larger than for an ordinary detector, increasing signal-to-noise ratio.

If the FIG. 3vacuum tube sensor3, with theelectron amplifier24, is employed with the PDAR imaging system depicted in FIG. 1, as before, laser light reflected from the target is captured by theoptics5 and focused on thesensor3. Laser photons are transferred by thewindow16 to thephotocathode17 where the laser light is converted to photoelectrons. If thevacuum tube sensor3, does not have a fiber optic window, light is focused, though thewindow16 on thephotocathode17 itself. The field E1 accelerates the photoelectrons into the top of theelectron amplifier24. A voltage across theelectron amplifier24 causes multiplication of the photoelectrons in theelectron amplifier24. The field E2 accelerates the electrons from the bottom of theelectron amplifier24 to theanodes23. The electron current is transferred from theanodes23 to their associated laser radar processor processing-electronics unit cells10. If the FIG. 3vacuum tube sensor3 does not contain anelectron amplifier24 but does containanodes23 the transfer of photons to electric current in the processing-electronics unit cells10 is essentially the same except there is no amplification. Theanode23 array is fabricated from the last metal layer of the laserradar processor chip8 or is a separate chip mechanically and electrically connected to the laserradar processor chip8. Theelectron amplifier24, is typically one or more microchannel plates.

An alternate-design FIG. 3vacuum tube sensor3 does not contain anamplifier24 nor ananode23 array. Instead the anode is a two-chip hybrid, adetector array6 mechanically and electrically connected to the laserradar processor chip8 as depicted in FIG.2. The hybrid replaces the laserradar processor chip8 in FIG.3. In this case the photoelectrons are accelerated by an electric field between thephotocathode17 and the anode, into thedetector array6, where the signal is amplified. Amplification results because it requires about three times the bandgap of the detector solid state material, or typically about 3 eV, to create an electron-hole pair and the potential drop between thephotocathode17 and the detector array is usually one or more keV. Although some energy is lost in penetrating into the active area of thedetectors7, the energy that remains will create multiple electron-hole pairs for each photoelectron and hence amplification. Charges that conduct to the bottom of thesubstrate14 are conducted through the conducting bump9 as an electric current to laser radar processor processing-electronics unit cells10 corresponding to thedetectors7 that absorbed the photoelectrons.

All the FIG. 3vacuum tube sensors3 can be used in a magnetic field oriented perpendicular to thephotocathode17. The magnetic field increases the spatial resolution of the invention by preventing lateral translation of photoelectrons emitted with velocity components parallel to the photocathode. The electrons spin around a magnetic field line in their transit to thedetector array6.

The detector or anode currents are processed by the laser radar processor processing-electronicsunit cell circuitry10, for allsensors3 as follows. Detector currents are input to theRTIA28 and converted to a voltage. The voltage output from the RTIA is separated into two legs, theTFR leg26 and theAR leg27. The first component in both legs is ahigh pass filter29 or34. The high pass filters29 and34 are important to reduce noise and increase signal-to-noise ratio. 1/f noise is largest at low frequency and thermal noise is flat in frequency space. Noise reduction and signal distortion are traded off in this component.

The purpose of theTFR leg26 is to measure the time, and hence the range, of the first return and to provide controlling input to theAR leg27. Range is measured by turning off theswitch39 when the voltage amplitude from theRTIA28, or equivalently the input current amplitude, is high enough. The voltage from the RTIA is filtered29, amplified30 and filtered31 again. All filtering reduces noise and increases signal-to-noise ratio. The voltage signal then enters aSchmitt Trigger32 which provides positive feedback for saturation to occur rapidly and therefore produces sharp rise times. Amplification and pulse shaping (and noise reducing filtering) is required to obtain a large enough, fast rising signal to trip the Memory33 (typically a flip-flop with amplification) and open theSwitch39.

Theswitch39 is connected to an Analog Memory (typically a capacitor) or a Range Counter (typically a modified high-speed shift register)40 in two alternative designs. The ramp voltage or a clock pulses pass through theSwitch39 vialine53 and this signal is terminated when theSwitch39 is opened by the first laser pulse return. The voltage on the capacitor is converted to time by knowledge of the ramp characteristics or the number of counts on the counter is directly related to time and this time determines the range of the first return via multiplication by the velocity of light.

TheMemory33 is triggered at the peak of the laser pulse for the weakest signal. Since it is not uncommon to have target reflection coefficients vary by an order of magnitude or more on the same target at the same range, the memory in different pixels could be triggered at the peak of the pulse in one pixel and near the beginning of the pulse in the second pixel. Thus if there were no amplitude correction processing (correcting for the measurable fact that a large amplitude laser pulse triggers theMemory33 closer to the beginning of the laser pulse than a smaller amplitude laser pulse), the uncertainty in range would be the pulse rise time. Amplitude correction for range is necessary for very accurate first-return range calculations for each pixel. The time of first return in each pixel is the basis for determining the times of all other returns. The time at which theMemory33 changes state, relative to the beginning of a given laser pulse shape, can be measured as a function of pulse amplitude. By knowledge of this function and by knowledge of the amplitude of the reflected laser pulse, all transit times and hence all ranges can be corrected for laser pulse amplitude.

The purpose of theAR leg27 is two fold. One branch, theAFR leg45, processes theRTIA28 signal voltage to determine a peak signal for the first return so that the range to the first-return object can be determined with high accuracy. Theprimary AR leg27 carries theRTIA28 signal voltage to the 3DI-UDARAmplitude Storage Circuitry43 where succeeding return signals can be stored. If the scenario timing is such that the first return signal can be stored in the 3DI-UDARAmplitude Storage Circuitry43 then the Peak Detector/Storage38 can be eliminated. Alternatively if, in practice, the laser pulse rise time is short enough, or the range accuracy requirement is not too severe, it may also be possible to eliminate the Peak Detector/Storage38. The Peak Detector/Storage38 contains timing circuitry that shuts it off, at a specific time, after theMemory33 is triggered so that other returns or reflections do not modify the peak signal. In one design the Peak Detector/Storage38 is a typical Peak Detector with a storage capacitor. The Peak Detector could be made with just four CMOS transistors for example: The input is on the gate of one transistor with the storage capacitor at the source. The two other transistors act as switches to reset the gate and the storage capacitor each cycle.

In an alternate design the Peak Detector/Storage38 is similar to the 3DI-UDARAmplitude Storage Circuitry43. In this latter Peak Detector/Storage38 design, signal amplitude is constantly stored on a sequence of capacitors. The time interval for switching from one capacitor to the next is fixed to be much smaller than the laser pulse rise time. When all the capacitors are charged, the first capacitor in the sequence is overwritten with the new amplitude voltage signals and so on. The trigger signal from theMemory33 turns on Peak Detector/Storage38 timing circuitry which terminates the serpentine sequence of capacitor charging in a time interval predetermined to include the signal peak. A typical number of capacitors in the sequence is20 and a typical capacitance is 0.25 pF for each storage capacitor.

With either Peak Detector/Storage circuitry38, the single capacitor storage or the multiple capacitor storage, theAFR leg45 is buffered37 to prevent feedback to thesensitive TFR leg26. Although the amplification chain for theRTIA28 voltage, thoughleg45, including the Peak Detector/Storage38, is not necessarily linear throughout the range of laser-generated input currents, the laser pulse amplitude can be found from the measured nonlinear relationship. Thus output of the Peak Detector/Storage38 can be used to find the amplitude of the laser pulse.

In themain AR leg27 theRTIA28 voltage is amplified35 and buffered36 and enters 3DI-UDARAmplitude Storage Circuitry43. This voltage varies in time as the laser photon pulse return signals vary in time. Buffering is required to prevent signals generated in the 3DI-UDARAmplitude Storage Circuitry43 from feeding back to theTFR leg26 and triggering theMemory38. As can be seen from U.S. Pat. No. 5,446,529, FIG. 5, the 3DI-UDARAmplitude Storage Circuitry43 consists of a series of capacitors that are sequentially charged. The Integration Time Clock determines switching time on the capacitors by means of a high-speed shift register; a clock pulse into the shift register causes the next capacitor in the sequence to be switched to the input line. The main difference between 3DI-UDARAmplitude Storage Circuitry43 in this invention and the associated circuitry in U.S. Pat. No. 5,446,529 is that the storage capacitors are never reset in the current invention. In the current invention the capacitors are linked to a voltage source, theRTIA28, rather than directly to theDetector7 orAnode23 which are current sources. Typical switching times can vary from 0.1 ns to 100 ns. Typically the number of storage capacitors in the 3DI-UDARAmplitude Storage Circuitry43 is 50 to 200.

TheDelay Counter42 determines when the capacitor charging begins. Amplitude storage could be going on all the time, as described above for the Peak Detector/Storage38, so that amplitude information prior to the triggering of theMemory33 is available, or capacitor charging (amplitude storage) could begin at a set time after theMemory33 is triggered. TheDelay Counter42 is set at system start up by the Pre-loadBin Count Control51 to stop the serpentine signal amplitude capture on the capacitors after a set time or set the time interval after the trigger of theMemory33 at which the signal amplitude capture and storage should begin on the capacitors. When theDelay Counter42 is set to start capacitor amplitude charging, after a certain time interval, charging is usually set to terminate when all capacitors have been charged.

After a time interval greater than the return time from the most distant target the Drive Electronics4 begins sequencing through the laser radar processor processing-electronics unit cells10, reading out the data. Each unit cell is selected in sequence byRow46 andColumn47 selection pulses and theOutput Amplifier41 is turned on. The 3DI-UDARAmplitude Storage Circuitry43 is set for read by the Read/Write andControl52. TheOutput Amplifier41 contains one or more amplifiers (typically source followers) and switches the data storage components to their respective output lines. TheOutput Amplifier41 drives the data signals to a chip output amplifier andmultiplexer12 which in turn drives the signals to the Drive and Output Electronics4.

The first-return Peak49 signal output from the Peak Detector/Storage38, the first-return Range48 output from the Analog Memory orCounter40 and all the target-reflection,Range Bin50 data from the 3DI-UDARAmplitude Storage Circuitry43 are processed by theimage processing computer4a.This data could be displayed as a 3D image or could be further processed to isolate targets. After the Drive and Output electronics4 has processed the laser radar processor processing-electronics unit cell10 output voltages, eachunit cell10 is reset by Drive Electronics4 generated pulses, making this processing-electronics unit cell ready for the next laser pulse.

Claims (106)

What is claimed is:

1. A device for imaging one or more three dimensional objects immersed in a light conducting medium comprising:

a pulsed light source;

means for transmitting light from said pulsed light source into said medium;

optics for collecting light from said medium during the time for light to transit from said pulsed light source, reflect from said objects and be collected by said optics;

a sensor means for detecting said collected light, said sensor means comprising

means for converting said collected light into electrical charge,

chip means comprising

multiplexing and chip output electronics,

a plurality of collection or detection means for collecting or detecting the electrical charge from said conversion means,

a plurality of unit cell processing electronics including memory units for storing data related to a first return transit time for a reflected laser pulse from a target pixel, and additional memory units for storing data related to the amplitude of laser pulse reflections from one or plurality of targets, including control circuitry by which the sampling time intervals of said memory units for storing data related to the amplitude of laser pulse reflections is independently controlled, from unit cell to unit cell and including output amplifier electronics adapted to provide signals to said multiplexing and chip output electronics,

drive electronics for providing voltages and for providing timing for said unit cell processing electronics, output amplifier electronics and said multiplexing and chip output electronics, and

output electronics for conditioning the signals from said memory units for data processing;

a computer for processing data from said output electronics.

2. The device for imaging one or more three dimensional objects immersed in a light conduction medium ofclaim 1 wherein said unit cell processing electronics, multiplexing and chip output electronics, and drive and output electronics is adapted to read out said data in real time between pulses from said light source.

3. The device for imaging one or more three dimensional objects immersed in a light conduction medium ofclaim 1 wherein said memory units for storing data related to a first return transit time are digital counters.

4. The device for imaging one or more three dimensional objects immersed in a light conduction medium ofclaim 1 wherein said memory units for storing data related to a first return transit time are capacitors.

5. The device for imaging one or more three dimensional objects immersed in a light conduction medium ofclaim 1 wherein said memory units for storing data related to a first return transit time are digital counters and capacitors.

6. The device for imaging one or more three dimensional objects immersed in a light conduction medium ofclaim 1 wherein the said data related to the first return transit time is obtained by means of disconnection from a ramp voltage.

7. The device for imaging one or more three dimensional objects immersed in a light conduction medium ofclaim 1 wherein the said data related to the first return transit time is obtained by means of disconnection from a series of clock pulses.

8. The device for imaging one or more three dimensional objects immersed in a light conduction medium ofclaim 1 wherein the said unit cell processing electronics contains a Schmitt Trigger and Memory means.

9. The device for imaging one or more three dimensional objects immersed in a light conduction medium ofclaim 6 wherein the said disconnection from a ramp voltage is caused by Schmitt Trigger and Memory means.

10. The device for imaging one or more three dimensional objects immersed in a light conduction medium ofclaim 7 wherein the said disconnection from a series of clock pulses is caused by Schmitt Trigger and Memory means.

11. The device for imaging one or more three dimensional objects immersed in a light conduction medium ofclaim 6 wherein the value of the said ramp voltage at disconnection is stored on a analog memory unit.

12. The device for imaging one or more three dimensional objects immersed in a light conduction medium ofclaim 11 wherein the said analog memory unit is a capacitor.

13. The device for imaging one or more three dimensional objects immersed in a light conduction medium ofclaim 7 wherein the number of said clock pulses at disconnection is stored on a digital memory unit.

14. The device for imaging one or more three dimensional objects immersed in a light conduction medium ofclaim 13 wherein the said digital memory unit is a pulse counter.

15. The device for imaging one or more three dimensional objects immersed in a light conduction medium ofclaim 1 wherein said conversion means is a solid state detector array.

16. The device for imaging one or more three dimensional objects immersed in a light conduction medium ofclaim 15 wherein the said solid state detector array is an array of avalanche photodiodes.

17. The device for imaging one or more three dimensional objects immersed in a light conduction medium ofclaim 15 wherein the said solid state detector array is a Mercury-Cadmium-Telluride detector array.

18. The device for imaging one or more three dimensional objects immersed in a light conduction medium ofclaim 15 wherein the said solid state detector array is a Indium-Gallium-Arsenide detector array.

19. The device for imaging one or more three dimensional objects immersed in a light conduction medium ofclaim 15 wherein the said solid state detector array is a silicon detector array.

20. The device for imaging one or more three dimensional objects immersed in a light conduction medium ofclaim 1 wherein said conversion means is a photocathode.

21. The device for imaging one or more three dimensional objects immersed in a light conduction medium ofclaim 1 wherein said conversion means and said chip means are contained in a vacuum tube.

22. The device for imaging one or more three dimensional objects immersed in a light conduction medium ofclaim 1 wherein said conversion means and said chip means are contained in a vacuum tube with an electron amplifier between them.

23. The device for imaging one or more three dimensional objects immersed in a light conduction medium ofclaim 22 wherein said electron amplifier is a microchannel plate.

24. The device for imaging one or more three dimensional objects immersed in a light conduction medium ofclaim 22 wherein said vacuum tube is situated in a magnetic field parallel to the tube axis.

25. The device for imaging one or more three dimensional objects immersed in a light conduction medium ofclaim 1 wherein said collection or detection means is an anode.

26. The device for imaging one or more three dimensional objects immersed in a light conduction medium ofclaim 1 wherein said collection or detection means is a diode.

27. The device for imaging one or more three dimensional objects immersed in a light conduction medium ofclaim 1 wherein said collection or detection means is a diode, a plurality of which are organized into one chip which are electrically and individually connected, by connection means, to the said unit cell processing electronics, a plurality of which are organized into a separate chip.

28. The device for imaging one or more three dimensional objects immersed in a light conduction medium ofclaim 1 wherein said collection or detection means is a anode, a plurality of which are organized into one chip which are electrically and individually connected, by connection means, to the said unit cell processing electronics, a plurality of which are organized into a separate chip.

29. The device for imaging one or more three dimensional objects immersed in a light conduction medium ofclaim 27 wherein said connection means are conducting bumps.

30. The device for imaging one or more three dimensional objects immersed in a light conduction medium ofclaim 1 wherein said collection or detection means is included in the said unit cell processing electronics.

31. The device for imaging one or more three dimensional objects immersed in a light conduction medium ofclaim 1 wherein the said unit cell processing electronics includes transimpedance amplifier means.

32. The device for imaging one or more three dimensional objects immersed in a light conduction medium ofclaim 1 wherein the said unit cell processing electronics includes amplifier means.

33. The device for imaging one or more three dimensional objects immersed in a light conduction medium ofclaim 1 wherein the said unit cell processing electronics includes filtering means.

34. The device for imaging one or more three dimensional objects immersed in a light conduction medium ofclaim 1 wherein the said unit cell processing electronics includes Peak Detector and Storage electronics.

35. The device for imaging one or more three dimensional objects immersed in a light conduction medium ofclaim 34 wherein the said Peak Detector and Storage electronics obtains the peak of the reflected laser light pulse.

36. The device for imaging one or more three dimensional objects immersed in a light conduction medium ofclaim 35 wherein the said peak of the reflected laser light pulse is stored on a capacitor.

37. The device for imaging one or more three dimensional objects immersed in a light conduction medium ofclaim 35 wherein the said Peak Detector and Storage electronics obtains and stores a time sequence of reflected laser light amplitude signals including the peak of the reflected laser light pulse.

38. The device for imaging one or more three dimensional objects immersed in a light conduction medium ofclaim 37 wherein the said time sequence of reflected laser amplitude signals including the peak of the reflected light signal are stored by charging a plurality of capacitors that are sequenced in time.

39. The device for imaging one or more three dimensional objects immersed in a light conduction medium ofclaim 38 wherein the said charging of a plurality of capacitors is sequenced in time by a shift register.

40. The device for imaging one or more three dimensional objects immersed in a light conduction medium ofclaim 1 wherein the said unit cell electronics includes means for terminating the information storage of said memory units after a time interval.

41. The device for imaging one or more three dimensional objects immersed in a light conduction medium ofclaim 1 wherein the said unit cell processing electronics contains buffers between the said memory units for storing data related to a first return transit time and the said additional memory units for storing data related to reflections from one or a plurality of targets.

42. The device for imaging one or more three dimensional objects immersed in a light conduction medium ofclaim 1 wherein the said additional memory units for storing data related to reflections from one or a plurality of targets are capacitors.

43. The device for imaging one or more three dimensional objects immersed in a light conduction medium ofclaim 42 wherein the said capacitors are sequentially charged.

44. The device for imaging one or more three dimensional objects immersed in a light conduction medium ofclaim 1 wherein the said unit cell electronics or the said drive electronics includes means for initiating the information storage of said memory units after a time interval and for terminating the information storage after a separate time interval.

45. The device for imaging one or more three dimensional objects immersed in a light conduction medium ofclaim 1, wherein said unit cell processing electronics includes switching means to turn amplifiers off during the laser interpulse period.

46. A sensor means for detecting collected light, said sensor means comprising

means for converting collected light into electrical charge,

chip means comprising

multiplexing and chip output electronics,

a plurality of collection or detection means for collecting or detecting the electrical charge from said conversion means,

a plurality of unit cell processing electronics including memory units for storing data related to a first return transit time for a reflected laser pulse from a target pixel, and additional memory units for storing data related to the amplitude of laser pulse reflections from one or plurality of targets, including control circuitry by which the sampling time intervals of said memory units for storing data related to the amplitude of laser pulse reflections are independently controlled, from unit cell to unit cell and including output amplifier electronics adapted to provide signals to said multiplexing and chip output electronics,

drive electronics for providing voltages and for providing timing for said unit cell processing electronics, output amplifier electronics and said multiplexing and chip output electronics, and

output electronics for conditioning the signals from said memory units for data processing;

a computer for processing data from said output electronics.

47. The sensor means for detecting collected light ofclaim 46 wherein said unit cell processing electronics, multiplexing and chip output electronics, and drive and output electronics is adapted to read out said data in real time between pulses from said light source.

48. The sensor means for detecting collected light ofclaim 46 wherein said memory units for storing data related to a first return transit time are digital counters.

49. The device detecting collected light ofclaim 46 wherein said memory units for storing data related to a first return transit time are capacitors.

50. The sensor means for imaging one or more three dimensional objects immersed in a light conduction medium ofclaim 46 wherein said memory units for storing data related to a first return transit time are digital counters and capacitors.

51. The sensor means for detecting collected light ofclaim 46 wherein the said data related to the first return transit time is obtained by means of disconnection from a ramp voltage.

52. The sensor means for detecting collected light ofclaim 46 wherein the said data related to the first return transit time is obtained by means of disconnection from a series of clock pulses.

53. The sensor means for detecting collected light ofclaim 46 wherein the said unit cell processing electronics contains a Schmitt Trigger and Memory means.

54. The sensor means for detecting collected light ofclaim 51 wherein the said disconnection from a ramp voltage is caused by Schmitt Trigger and Memory means.

55. The sensor means for detecting collected light ofclaim 52 wherein the said disconnection from a series of clock pulses is caused by Schmitt Trigger and Memory means.

56. The sensor means for detecting collected light ofclaim 51 wherein the value of the said ramp voltage at disconnection is stored on an analog memory unit.

57. The sensor means for detecting collected light ofclaim 56 wherein the said analog memory unit is a capacitor.

58. The sensor means for detecting collected light ofclaim 52 wherein the number of said clock pulses at disconnection is stored on a digital memory unit.

59. The sensor means for detecting collected light ofclaim 58 wherein the said digital memory unit is a pulse counter.

60. The sensor means for detecting collected light ofclaim 46 wherein said conversion means is a solid state detector array.

61. The sensor means for detecting collected light ofclaim 60 wherein the said solid state detector array is an array of avalanche photodiodes.

62. The sensor means for detecting collected light ofclaim 60 wherein the said solid state detector array is a Mercury-Cadmium-Telluride detector array.

63. The sensor means for detecting collected light ofclaim 60 wherein the said solid state detector array is an Indium-Gallium-Arsenide detector array.

64. The sensor means for detecting collected light ofclaim 60 wherein the said solid state detector array is a silicon detector array.

65. The sensor means for detecting collected light ofclaim 46 wherein said conversion means is a photocathode.

66. The sensor means for detecting collected light ofclaim 46 wherein said conversion means and said chip means are contained in a vacuum tube.

67. The sensor means for detecting collected light ofclaim 46 wherein said conversion means and said chip means are contained in a vacuum tube with an electron amplifier between them.

68. The sensor means for detecting collected light ofclaim 67 wherein said electron amplifier is a microchannel plate.

69. The sensor means for detecting collected light ofclaim 67 wherein said vacuum tube is situated in a magnetic field parallel to the tube axis.

70. The sensor means for detecting collected light ofclaim 46 wherein said collection or detection means is an anode.

71. The sensor means for detecting collected light ofclaim 46 wherein said collection or detection means is a diode.

72. The sensor means for detecting collected light ofclaim 46 wherein said collection or detection means is a diode, a plurality of which are organized into one chip which are electrically and individually connected, by connection means, to the said unit cell processing electronics, a plurality of which are organized into a separate chip.

73. The sensor means for detecting collected light ofclaim 46 wherein said collection or detection means is a anode, a plurality of which are organized into one chip which are electrically and individually connected, by connection means, to the said unit cell processing electronics, a plurality of which are organized into a separate chip.

74. The sensor means for detecting collected light ofclaim 72 wherein said connection means are conducting bumps.

75. The sensor means for detecting collected light ofclaim 46 wherein said collection or detection means is included in the said unit cell processing electronics.

76. The sensor means for detecting collected light ofclaim 46 wherein the said unit cell processing electronics includes transimpedance amplifier means.

77. The sensor means for detecting collected light ofclaim 46 wherein the said unit cell processing electronics includes amplifier means.

78. The sensor means for detecting collected light ofclaim 46 wherein the said unit cell processing electronics includes filtering means.

79. The sensor means for detecting collected light ofclaim 46 wherein the said unit cell processing electronics includes Peak Detector and Storage electronics.

80. The sensor means for detecting collected light ofclaim 79 wherein the said Peak Detector and Storage electronics obtains the peak of the reflected laser light pulse.

81. The sensor means for detecting collected light ofclaim 80 wherein the said peak of the reflected laser light pulse is stored on a capacitor.

82. The sensor means for detecting collected light ofclaim 80 wherein the said Peak Detector and Storage electronics obtains and stores a time sequence of reflected laser light amplitude signals including the peak of the reflected laser light pulse.

83. The sensor means for detecting collected light ofclaim 81 wherein the said time sequence of reflected laser amplitude signals including the peak of the reflected light signal are stored by charging a plurality of capacitors that are sequenced in time.

84. The sensor means for detecting collected light ofclaim 82 wherein the said charging of a plurality of capacitors is sequenced in time by a shift register.

85. The sensor means for detecting collected light ofclaim 46 wherein the said unit cell electronics includes means for terminating the information storage of said memory units after a time interval.

86. The sensor means for detecting collected light ofclaim 46 wherein the said unit cell processing electronics contains buffers between the said memory units for storing data related to a first return transit time and the said additional memory units for storing data related to reflections from one or a plurality of targets.

87. The sensor means for detecting collected light ofclaim 46 wherein the said additional memory units for storing data related to reflections from one or a plurality of targets are capacitors.

88. The sensor means for detecting collected light ofclaim 86 wherein the said capacitors are sequentially charged.

89. The sensor means for detecting collected light ofclaim 46 wherein the said unit cell electronics includes means for initiating the information storage of said memory units after a time interval and for terminating the information storage after a separate time interval.

90. The sensor means for detecting collected light ofclaim 46, wherein said unit cell processing electronics includes switching means to turn amplifiers off during the laser interpulse period.

91. A method for imaging one or more three dimensional objects obscured by reflective or absorptive material but otherwise immersed in a light conducting medium comprising the steps of:

generating a series of pulses of light;

transmitting said light into said medium to the source of obscuration;

collecting light from said source of obscuration during the time of transmission and reflection of light from said source of obsuration;

detecting said collected light

providing timing control from said detected light

providing electrical signals from a plurality of positions on the objects beyond the source of obscuration with a single light pulse,

storing said electrical signals on a plurality of unit cells corresponding to the said plurality of positions on said objects,

providing signals from said storage means,

converting the signals stored on said storage means to a three-dimensional image of the objects.

92. A method for imaging one or more three dimensional objects obscured by reflective or absorptive material but otherwise immersed in a light conducting medium ofclaim 90 wherein the electrical signals correspond to a time sequence of the amplitudes of the reflected light.

93. The device for imaging one or more three dimensional objects immersed in a light conduction medium ofclaim 8 wherein the disconnection from a ramp voltage is caused by the said Schmitt Trigger and Memory means.

94. The device for imaging one or more three dimensional objects immersed in a light conduction medium ofclaim 8 wherein the disconnection from a series of clock pulses is caused by the said Schmitt Trigger and Memory means.

95. The device for imaging one or more three dimensional objects immersed in a light conduction medium ofclaim 28 wherein said connection means are conducting bumps.

96. The device for imaging one or more three dimensional objects immersed in a light conduction medium ofclaim 38 wherein the said unit cell electronics includes means for terminating the charging of said capacitors after a time interval.

97. The device for imaging one or more three dimensional objects immersed in a light conduction medium ofclaim 42 wherein the said unit cell electronics includes means for initiating the charging of said capacitors after a time interval and for terminating the charging after a separate time interval.

98. The sensor means for detecting collected light ofclaim 53 wherein disconnection from a ramp voltage is caused by the said Schmitt Trigger and Memory means.

99. The sensor means for detecting collected light ofclaim 53 wherein disconnection from a series of clock pulses is caused by the said Schmitt Trigger and Memory means.

100. The sensor means for detecting collected light ofclaim 73 wherein said connection means are conducting bumps.

101. The sensor means for detecting collected light ofclaim 83 wherein the said unit cell electronics includes means for terminating the charging of said capacitors after a time interval.

102. The sensor means for detecting collected light ofclaim 87 wherein the said unit cell electronics includes means for initiating the charging of said capacitors after a time interval and for terminating the charging after a separate time interval.

103. The device for imaging one or more three dimensional objects immersed in a light conduction medium ofclaim 22 wherein said electron amplifier is a diode array electrically connected to the readout array and impact ionization in the diode array is the amplification means.

104. The device for imaging one or more three dimensional objects immersed in a light conduction medium ofclaim 1 wherein the said unit cell and processing electronics includes digital storage means for obtaining the transit time to the target and includes means to store a time sequence of reflected laser light amplitude signals not including the peak of the reflected laser light pulse.

105. The sensor means for detecting collected light ofclaim 67 wherein said electron amplifier is a diode array electrically connected to the readout array and impact ionization in the diode array is the amplification means.

106. The sensor means for detecting collected light ofclaim 46 wherein the said unit cell and processing electronics includes digital storage means for obtaining the transit time to the target and includes means to store a time sequence of reflected laser light amplitude signals not including the peak of the reflected laser light pulse.

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